The present invention relates to a process camera which is easy to handle, is compact so that it only takes up a small space, and can be used in a fully bright environment, and more particularly to a process camera suitable for imposing multiple-page copy images on a large photosensitive medium for platemaking.
Various process cameras for imposing copy images made up of many pages are known from U.S. Pat. Nos. 3,998,546, 3,837,742, and 3,920,333, for example. According to the disclosed process cameras, a copyboard for holding a copy to be photographed and a platen for supporting a photosensitive medium are vertically disposed in confronting relation. When a copy and a photosensitive medium are to be placed on the copyboard and the platen, respectively, the copy and the photosensitive medium must be held vertically and attached to the copyboard and the platen which extend vertically. Therefore, it is troublesome to handle the copy and the photosensitive medium when they are to be set on the copyboard and the platen. In order to maintain a desired optical path length from the copyboard to the platen, it is necessary to keep the copyboard and the platen spaced from each other by a certain long distance. With the copyboard and the platen being thus spaced widely from each other, the entire process camera is long and takes up a large installation space.
Japanese Utility Model Application No. 62(1987)-93665 filed by the applicant of the present application discloses a process camera which employs a mirror to bend an optical path. The mirror allows the image of a copy on a horizontal copyboard to be projected onto a photosensitive medium on a vertical platen. Therefore, the copy can easily be handled when it is attached to the copyboard. Another advantage is that the overall length of the camera is small as the optical path is bent by the mirror.
In each of the conventional process cameras described above, however, since at least the platen is placed horizontally, a photosensitive medium should be handled with the aid of a highly reliable suction device so that the photosensitive medium will not fall off the platen. Accordingly, it is still troublesome and inconvenient to handle the photosensitive medium at the time it is to be attached to the platen. The process cameras are considerably long, and much remains to be improved to make them more compact. The process camera proposed by the applicant employs a lens and a single mirror, and lends itself to the production of a direct press plate because they can produce a positive image.
If a photosensitive medium produces a negative image, however, the negative image must be converted to a reversed image. To this end, there is used a process camera in which a copy and a photosensitive medium are vertically disposed in confronting relation to each other with a focusing lens interposed therebetween, as disclosed in the U.S. Patents referred to above. The process cameras disclosed in the above U.S. Patents do not have any means for confirming the position of the copy, and suffer difficulty in positioning the copy. Stated otherwise, since there is no means for confirming the position of the copy, the copy and the photosensitive medium are vertically arranged in confronting relation to each other to facilitate the positioning of the copy.
If a direct press plate is used as a photosensitive medium in the conventional process camera which imposes multiple-page copy images, then it is difficult to photograph back signatures and other marks on non-image areas outside the pages. These marks have heretofore been photographed by contact printing in a printer. More specifically, a portion of the process camera which includes the platen is placed in a dark room in which a printer, an image developing machine, etc. are disposed. After a copy having a certain number of pages has been photographed on a photosensitive medium by the process camera, the photosensitive medium is removed from the process camera, and set on the printer. On the printer, a masking sheet of paper is placed over the photosensitive medium. The masking sheet has an area for shielding photographed copy images from light and marks to be printed in non-image areas between the copy images. The masking sheet is superposed on the photosensitive medium and held in registration therewith by pins inserted in perforations defined in the maksing sheet and the photosensitive medium, and the marks on the masking sheet are printed on the non-image areas by contact printing in the printer. The copy images which have been photographed by the process camera remain on the photosensitive medium, and the marks which include back signatures and other outside-page information marks are printed on the non-image areas. Unwanted portions of the non-image areas are exposed to light. The photosensitive medium with the necessary marks printed is then processed by the image developing machine which develops the copy images, whereupon a direct press plate is completed.
When a positive-negative photosensitive medium is employed, other areas than photographed copy images on the photosensitive medium are not exposed to light. If the copy images on the photosensitive medium were developed and used directly to produce a printing plate, non-image areas outside of the pages would be printed. To avoid such a drawback, it is necessary to either expose the non-image areas outside of the pages to light or apply a separate mask to the photosensitive medium when a printing plate is produced from the photosensitive medium. In a dark room, a masking sheet of paper is placed on the photosensitive medium and printed by direct printing in a printer, and the non-image areas are exposed to light.
Irrespective of the type of a photosensitive medium used, therefore, it has to be processed by the direct printing process in a printer placed in a dark room in order to print back signatures and other marks on non-image areas or expose the non-image areas to light. Since the direct printing process is manually carried out, it is tedious, time-consuming, and inefficient.
In view of the aforesaid shortcomings, the applicant has proposed a process camera by which necessary outside-page information marks are automatically photographed on a photosensitive medium after a multiple-page copy has been photographed thereon, as disclosed in Japanese Patent Application No. 63(1988)-122543. According to the proposed process camera, no manual operation is required in a dark room, the process camera is easy to handle, and highly efficient.
In the proposed process camera, a platen with a photosensitive medium mounted thereon is moved along two perpendicular axes within the plane of the photosensitive medium until a photographing position on the photosensitive medium is established. A range or area in which an image is to be photographed on the photosensitive medium is selected by independently moving two pairs of, i.e., four, mask plates along the above axes in front of the photosensitive medium set on the platen.
The mask plates are however not moved while in intimate contact with the photosensitive medium on the platen, but a gap or clearance exists between each of the mask plates and the photosensitive medium. Since the photosensitive medium can automatically be set on and removed from the platen, the clearance between the mask plates and the photosensitive medium is large so as to provide enough space for allowing a photosensitive medium carrier to move between the platen and the mask plates. Therefore, the positions of the mask plates are not determined by only photographing dimensions at the time, but vary depending on various photographing conditions such as the distance between the photosensitive medium and the mask plates, the photographing magnification, the focal length of the focusing lens, etc. The positions to which the mask plates are to move must be independently determined because the distances from the platen to the respective mask plates differ from each other to avoid physical interference between the mask plates.